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Before you take your graded quiz, try the practice activity below.

A statement that appears to be true but has not yet been proved is a ______.

  1. counterexample
  2. guess
  3. conjecture
  4. proof

A statement that appears to be true but has not yet been proved is a conjecture.

A statement that appears to be true but has not yet been proved is a conjecture.

A statement that appears to be true but has not yet been proved is a conjecture.

A statement that appears to be true but has not yet been proved is a conjecture.

An example showing that a conjecture is not true is called a _____.

  1. false statement
  2. proof
  3. formal proof
  4. counterexample

An example showing that a conjecture is not true is called a counterexample.

An example showing that a conjecture is not true is called a counterexample.

An example showing that a conjecture is not true is called a counterexample.

An example showing that a conjecture is not true is called a counterexample.

Showing some specific examples that are true for a conjecture shows that it is always true.

  1. true
  2. false

Specific examples may show that a conjecture is true some of the time, but a formal proof is necessary to prove a conjecture is always true.

Specific examples may show that a conjecture is true some of the time, but a formal proof is necessary to prove a conjecture is always true.

Which of the following would prove that the given conjecture is always true?

Conjecture: The sum of two consecutive integers is an odd number.

  1. First number = x, second number = x + 1.
    Sum = (x) + (x + 1) = 2x + 1
  2. First number = 10, second number = 11.
    Sum = (10) + (11) = 21
  3. First number = 100, second number = 200.
    Sum = (100) + (200) = 300
  4. This is not a true conjecture.

Sum = (x) + (x + 1) = 2x + 1 proves the conjecture by taking any two consecutive numbers into account.

Sum = (x) + (x + 1) = 2x + 1 proves the conjecture by taking any two consecutive numbers into account.

Sum = (x) + (x + 1) = 2x + 1 proves the conjecture by taking any two consecutive numbers into account.

Sum = (x) + (x + 1) = 2x + 1 proves the conjecture by taking any two consecutive numbers into account.

Summary

Questions answered correctly:

Questions answered incorrectly: